The present invention relates to magnetoresistive head assemblies. In particular, the present invention relates to a method and apparatus for reducing charge build-up on a magnetoresistive sensor element of the magnetoresistive head assembly.
Magnetoresistive head assemblies are used in magnetic storage systems to detect magnetically encoded information on specially prepared recording media such as magnetic discs. A magnetoresistive head assembly includes a magnetoresistive transducer or sensor element electrically connected to detection circuitry by at least two electrical conductors. The magnetoresistive sensor element has a resistance which modulates in response to changing magnetic fields corresponding to magnetically encoded information on the media. The detection circuitry detects the resulting change in resistance by passing a sense current through the electrical conductors and through the magnetoresistive sensor element and by measuring the voltage drop across the magnetoresistive sensor element. The resulting voltage signal is used to recover information from the medium.
Typically, the magnetoresistive sensor element is formed or fabricated as part of a wafer which is severed into a plurality of sliders. A magnetic writerxe2x80x94generally of the inductive typexe2x80x94is also integrated with the sensor during wafer fabrication. The slider carries the magnetoresistive sensor and writer elements adjacent to the surface of the magnetic storage medium. Together, the magnetoresistive sensor, the inductive writer, and the slider constitute what is called a magnetoresistive head. The slider of the magnetoresistive head is supported above the magnetic storage medium as part of an arm assembly or as part of an E-block assembly. The arm assembly typically includes a support arm, a load beam or spring, a gimbal and the magnetoresistive head. The support arm carries the load beam and the load beam is attached to the gimbal. Lastly, the gimbal is preferably coupled to the slider of the magnetoresistive head. The support arm, load beam and gimbal support and carry the magnetoresistive head adjacent a magnetic storage medium such as a magnetic disc.
The first and second electrical conductors electrically connecting the magnetoresistive sensor element and the detection circuitry typically comprise conductive traces, bonding pads and electrical wires. The conductive traces extend along a surface of the slider and electrically interconnect the magnetoresistive sensor element and the bonding pads. The bonding pads are electrically connected to the magnetoresistive sensor element by the conductive traces and are located on a surface of the slider. The bonding pads provide a surface by which electrical conductors such as wire may be attached to electrically connect detection circuitry and the magnetoresistive sensor. The wires are typically tacked or bonded to the bonding pads and to at least one surface of the slider. The wires further extend along the gimbal, the load beam and the arm to the detection circuitry. These wires can be carried on a flexible carrier such as polyimide.
Electrostatic energy which is conducted or discharged to the magnetoresistive sensor element by direct electrical continuity or dielectric breakdown may possibly damage the magnetoresistive sensor element. Electrostatic energy may be generated any time during the fabrication, assembly, testing and shipment of the disc drive including fabrication of the magnetoresistive head assembly of the head/gimbal assembly, assembly of the E-block assembly of the final disc drive, electrical testing of components and shipment of the components or the disc drive. In response, various procedures and equipment have been installed to control electrostatic discharge (ESD) levels during every stage of handling through final disc drive assembly to prevent damage to the magnetoresistive sensor element caused by ESD. Some ESD handling procedures and equipment can limit or reduce the discharge energy delivered to the magnetoresistive head. However, due to the continual drive to increase storage density in magnetic disc drive units, magnetoresistive sensor elements have become increasingly more sensitive. Because of the decreasing dimensions of advanced magnetoresistive heads and the thinner films used in magnetoresistive sensor elements, electrostatic discharge damage threshold is rapidly falling below the limits that can be controlled through environmental controls. Further, these techniques are expensive and typically require additional processing steps that can reduce yields.
The present invention provides a solution to this and other problems and offers advantages over the prior art.
The present invention relates to magnetoresistive sensors or transducer assemblies which have bleed resistors to address the above-mentioned problems.
In accordance with one embodiment of the present invention, a magnetoresistive transducer is provided which includes a substrate, an insulating layer on the substrate and a magnetoresistive assembly on the insulating layer. At least one bleed resistor is coupled between the magnetoresistive assembly and the substrate. The bleed resistor has a relatively large electrical resistance and provides a path to discharge electrostatic build up without impacting performance.
These and various other features as well as advantages which characterize the present invention will be apparent upon reading the following detailed description and review of the associated drawings.